The present invention relates to the testing of a semiconductor wafer and, more particularly, to providing an electrical connection to the backside of the wafer.
During the testing of semiconductor wafers it is often desirable to force the semiconductor bulk (e.g., silicon) to a particular potential. This is typically accomplished by using a sharp electrical contact to scratch through the oxide layer on some portion of the wafer.
This scratching process does not lend itself well to the automated testing of wafers, particularly in the case of thick oxides which may be, for example, as much as a micron in thickness. Even using contacts of tungsten carbide, the point of the contact is quickly dulled or even broken.
The problem is further complicated by the difficulty of determining if an ohmic connection has been made where the tests being performed are otherwise contactless. In this case, direct measurement of the quality of the connection would require an additional contact to be made to allow a resistance value to be measured between the contacts.